Metallurgical furnace

Abstract

A metallurgical furnace is disclosed which carries out the several steps involved in the liquid phase sintering of preforms of powdered metals, ceramics, and/or combinations of these materials. The metallurgical furnace comprises a pressure vessel defining an interior pressure chamber and a main furnace which is contained within the pressure chamber and spaced inwardly from the walls of the pressure vessel. The main furnace comprises a bottom wall, side walls, top wall and end walls which together form a substantially closed furnace chamber. Each of these furnace walls comprises at least one layer of insulation and, in addition, the top, sides, and end walls further include a vapor barrier which minimizes convection within the furnace chamber. The metallurgical furnace according to the present invention is capable of performing the presinter, sinter and hot isostatic pressing of preforms within the furnace chamber.

I claim: 
     
       1. A device for liquid phase sintering of preforms, said preforms initially comprising powdered material cohesively held together by a fugitive binder, said device comprising: a pressure vessel defining an interior pressure chamber;   a furnace contained within said pressure chamber, said furnace comprising a top wall, a bottom wall and side and/or end walls which together form a substantially closed furnace chamber, said top wall and each side and/or end wall having a predefined area,   each of said furnace walls comprising at least one layer of thermal insulation,   said furnace top wall and each of said furnace side and/or end walls comprising a vapor barrier which extends across the entire area of its respective top, side and/or end wall,   means for heating said furnace chamber and furnace walls above the vaporization temperature of the fugitive binder,   means for enabling a gas to escape through said bottom wall,   means for condensating vaporized fugitive binder on the pressure vessel,   means for selectively providing access to said furnace chamber, and   means for pressurizing said interior pressure chamber.   
     
     
       2. The invention as defined in claim 1 wherein each of said side and/or end walls comprise two layers of insulation and wherein said vapor barrier is sandwiched in between said insulation layers. 
     
     
       3. The invention as defined in claim 1 wherein said bottom wall is constructed of porous insulation and wherein said device comprising means for evacuating said pressure chamber and said furnace chamber. 
     
     
       4. The invention as defined in claim 1 and comprising means for introducing a wash gas directly into said furnace chamber. 
     
     
       5. The invention as defined in claim 4 wherein said introducing means comprises an elongated distribution tube secured within said furnace chamber, said tube having a plurality of axially spaced ports formed along its length and means for supplying said wash gas to said tube. 
     
     
       6. The invention as defined in claim 1 and comprising means for cooling said pressure vessel below the liquification temperature of the fugitive binder. 
     
     
       7. The invention as defined in claim 6 wherein said cooling means comprises a water cooled fluid system in contact with said pressure vessel. 
     
     
       8. A device for liquid phase sintering of preforms, said preforms initially comprising powdered material cohesively held together by a fugitive binder, said device comprising: a pressure vessel defining an interior pressure chamber;   a furnace contained within the said pressure chamber, said furnace comprising a top wall, a bottom wall and side and/or end walls which together form a substantially closed furnace chamber,   each of said furnace walls comprising at least one layer of thermal insulation,   said bottom wall being constructed of porous insulation to thereby enable a gas to escape,   each of said furnace top, side and/or end walls comprising a vapor barrier,   means for heating said furnace chamber and furnace walls above the vaporization temperature of the fugitive binder,   means for condensating vaporized fugitive binder on the pressure vesel,   means for selectively providing access to said furnace chamber,   means for evacuating said pressure chamber to said furnace chamber.   
     
     
       9. The invention as defined in claim 8 wherein each of said side and/or end walls comprises a vapor barrier. 
     
     
       10. The invention as defined in claim 9 wherein said side and/or end walls comprise two layers of insulation and wherein said vapor barrier is sandwiched in between said insulation layers. 
     
     
       11. The invention as defined in claim 8 and comprising means for selectively pressurizing said furnace chamber. 
     
     
       12. A device for liquid phase sintering of preforms, said preforms initially comprising powdered material cohesively held together by a fugitive binder, said device comprising: a pressure vessel defining an interior pressure chamber;   a furnace contained within said pressure chamber, said furnace comprising a top wall, a bottom wall and side and/or end walls which together form a substantially closed furnace chamber,   each of said furnace walls comprising at least one layer of thermal insulation,   each of said furnace top, side and/or end walls comprising a vapor barrier,   means for heating said furnace chamber and furnace walls above the vaporization temperature of the fugitive binder,   means for enabling a gas to escape through said bottom wall,   means for condensating vaporized fugitive binder on the pressure vessel,   means for selectively providing access to said furnace chamber,   means for cooling said pressure vessel below the liquification temperature of the fugitive binder, and   wherein said cooling means comprises a water cooled fluid system in contact with said pressure vessel.   
     
     
       13. A device for liquid phase sintering of preforms, said preforms initially comprising powdered material cohesively held together by a fugitive binder, said device comprising: a pressure vessel defining an interior pressure chamber;   a furnace contained within said pressure chamber, said furnace comprising a top wall, a bottom wall and side and/or end walls which together form a substantially closed furnace chamber,   each of said furnace walls comprising at least one layer of thermal insulation,   each of said furnace top, and/or end walls comprising a vapor barrier,   means for heating said furnace chamber and furnace walls above the vaporization temperature of the fugitive binder,   means for enabling a gas to escape through said bottom wall,   means for condensating vaporized fugitive binder on the pressure vessel,   means for selectively providing access to said furnace chamber,   means for introducing a wash gas directly into said furnace chamber,   a pressure responsive valve having an inlet open to said pressure chamber and an outlet open exteriorly of said pressure vessel, and   means for igniting gases exhausted from said valve outlet.   
     
     
       14. A device for liquid phase sintering of preforms, said preforms initially comprising powdered material cohesively held together by a fugitive binder, said device comprising: a pressure vessel defining an interior pressure chamber;   a furnace contained within said pressure chamber, said furnace comprising a top wall, a bottom wall and side and/or end walls which together form a substantially closed furnace chamber, said top wall and each side and/or each wall having a predefined area,   each of said furnace walls comprising at least one layer of thermal insulation,   said furnace top wall and each of said furnace side and/or end walls comprising a vapor barrier which extends across the entire area of its respective top, side and/or end wall,   means for heating said furnace chamber and furnace walls above the vaporization temperature of the fugitive binder,   means for enabling a gas to escape from said furnace chamber,   means for condensating vaporized fugitive binder on the pressure vessel,   means for selectively providing access to said furnace chamber, and   means for pressurizing said interior pressure chamber.